Early Adulthood Inflammation May Influence Cognition in Midlife

When you get injured or become sick, the body rounds up its army of inflammatory compounds to go to work and start healing the injury or illness. This is called acute inflammation and it’s a necessary part of the healing process. 

But there’s another type of inflammation that’s not so necessary that attacks healthy tissue in the body. Chronic inflammation hangs out in the body due to things like ongoing, long-term stress, lack of quality sleep, smoking, lack of physical activity, obesity and even chemicals in food. This is the type of inflammation that is a culprit behind many health issues, including arthritis, heart disease, cancer and diabetes.

Chronic inflammation is also linked with dementia and Alzheimer’s disease. And while many studies on cognition focus on inflammation levels later in life, a new study published on July 3, 2024 in Neurology highlights the need to start preventing and treating chronic inflammation in early adulthood to help prevent cognitive decline later in life. Let’s dig in. 

How Was This Study Conducted?

Researchers from the University of California San Francisco used data from the CARDIA study, a long-term study with the goal of identifying factors in young adulthood that lead to heart disease later in life. There were 2,364 participants, about 55% of them female. Participants were 18 to 30 years old at the beginning of the study. 

Demographic information was collected, including factors that would be used as covariates and adjusted for when statistical analyses were run. This included a history of depression, alcohol use, smoking status, physical activity and body mass index (BMI). Participants were also tested in year 7 of the study for a gene that puts people at higher risk for Alzheimer’s disease.

During the first 18 years of the study, participants were tested four times several years apart via blood draw for the inflammatory marker C-reactive protein (CRP). CRP is an indication of the level of inflammation in the body. Participants also took several cognitive tests 5 years after the last CRP blood test. This was all to determine whether there was a link between inflammation levels during early adulthood and cognitive abilities later in life. 

Based on bloodwork results for CRP, participants were placed into one of three groups called inflammation trajectories: lower stable CRP, moderate/increasing CRP or consistently higher CRP. Of the 2,364 participants, 39% had consistently higher CRP levels, 16% had moderate/increasing CRP and 45% had lower stable CRP. 

Researchers were then able to connect each participant’s inflammation trajectory with each cognitive test they took to see if there was a connection between levels of inflammation and various factors of cognitive functioning. 

What Did This Study Show & How Can You Apply It to Real Life?

In short, participants with higher levels of inflammation, including moderate/increasing inflammation, during early adulthood had higher odds of poor cognitive function in midlife.

Specifically, those with moderate/increasing CRP and consistently higher CRP had more than 2 times greater odds of poor performance in processing speed compared to the lower stable CRP group. Processing speed is how quickly the brain can receive, understand and respond to information. The odds were about the same for executive functioning—higher-level cognitive skills used to control and coordinate other cognitive abilities and behaviors. 

It’s important to keep in mind that the cognitive tests were not being given to 80-year-olds. These participants were in their early 40s to late 50s when their cognition was tested—which emphasizes that the changes in the brain begin earlier in life. 

“We know from long-term studies that brain changes leading to Alzheimer’s disease and other dementias may take decades to develop,” says the study’s lead author Amber Bahorik, Ph.D., of the UCSF Department of Psychiatry and Behavioral Sciences and the Weill Institute for Neurosciences in a press release. “We wanted to see if health and lifestyle habits in early adulthood may play a part in cognitive skills in midlife, which in turn may influence the likelihood of dementia in later life.”

This study also emphasizes the need for prevention. We know that certain lifestyle factors influence inflammation so it’s important to focus on lifestyle behaviors you can change—stress, sleep, physical activity and diet. And while obesity is a risk factor for inflammation, it is not a behavior. It’s more important to focus on the health habits that influence weight—which just so happen to be the same ones that influence inflammation.

The Bottom Line

This study suggests that moderate/increasing and higher inflammation levels during early adulthood may negatively influence cognitive abilities during midlife. This may, in turn, place you at a higher risk of developing cognitive disorders, like Alzheimer’s disease, later in life. And while genetics do play a role in inflammation and brain disorders, so do lifestyle behaviors. If you smoke, seek support to help you quit. If you drink alcohol, make sure you’re sticking to moderate amounts of it—consuming higher amounts of alcohol has been linked to inflammation. Move your body more often, get a handle on your stressors, shut your devices down so you can get more quality sleep and start incorporating more anti-inflammatory foods into your diet. If you want to go all-in, you could follow the MIND diet, an eating pattern designed specifically for brain health.